(a) Field of the Invention
The present invention relates to a sealing machine of clip type for plastic film products (e.g. a plastic bag), and more particularly to one in appearance similar to that of a stationary or laundry clip, allowing portable in use by omitting a transformer in circuit.
(b) Description of the Prior Art
For objects such as plastic materials, crops and even the edibles wrapped up or placed in plastic film or bag for storage, up-scaling industrial or commercial purpose thermal sealing machines have been available for years. However, those sealing machines, desktop or seat type, take larger space and provide less mobility, if any, preventing home application. However, clothes, edibles (e.g. home baked cookies), kitchen remains, or perishable refuses generated in our daily life, objects pending sorting for storage (e.g. stationary items, toys or umbrella) also significantly depend on the use of a thermal sealing machine. Pratically, no one would bother using a sealing machine for domestic purpose since the conventional sealing machine is not portable.
A conventional sealing machine used a flat band of NiCd resistance wire as heater conductor (approximately in 5 mm wide, and 0.1 mm thick) and its resistance is approximately 0.6xcexa9 for a sealing machine with 200 mm long heater wire. If 15V/20 A power is used, a 300W, weighing 2 Kg transformer must be used to drop city power voltage (say 100V) to 15V. Saving said transformer, when the heater wire is connected to 100V source, approximately 170 A current will be conducted to immediately burn out the heater wire. To maintain the current at 20 A, the voltage must be dropped to 15V or having the heater wire extended for 1200 mm long.
As described above, the transformer is used for producing a drop. Accordingly, the comparatively heavy weight of the transformer and more sturdy structure required to support the thinner heater wire prevent the conventional sealing machine from being compact for hand-held operation, thus, from becoming one of the home electrical appliances.
Furthermore, should longer heater wire be used, the extra length of the heater wire must be wound back and forth for multiple rounds on non-process surface, resulting in overheated heater wire particularly at both ends of the section of the heater wire on the process surface. Besides, said both ends could easily melt though the plastic film or bag during the process of sealing, forming missealing or weak spot on the sealing. Finally, the winding of the heater wire is vulnerable to failure.
The primary purpose of the present invention is to provide a compact sealing machine of clip type allowing hand-held operation essentially comprised of a trough, a press plate, a pressure providing device, a heater element and a circuit board. To achieve the purpose, the heater element is provided inside the trough. A portion extending from one side of the trough is extended to accommodate said circuit board. A pivot provided on said extension to connect to the handle of said press plate. A silicon rubber stick provided beneath said press plate holds against said heater element in the trough when the press plate is pressed while the pressure device provided between said trough and press plate always holds against the heater element in the trough. The section of the heater element indicates semi-circular and is connected at its end to a cooling electrode. Said circuit board comprised of surge absorption capacitor, tantalum capacitor, diode, gate transistor, and transistor, as a minimum is connected to the heater element to introduce a drop for the use by the heater element.